Hydraulic actuator having cooling fluid circulation



2,955,574 HYDRAULIC ACTUATOR HAVING COOLING FLUID CIRCULATION Filed Jan.13, 1958 H. M. GEYER Oct. 11, 1960 4 Sheets-$heet 1 INVENTOR. flowaea MGame Ms firms/m 2,955,574 HYDRAULIC ACTUATOR HAVING COOLING FLUIDCIRCULATION Filed Jan. 15, 1958 I H. M. GEYER 4 Sheets-Sh et 2 Oct. 11,1960 I-NVENTOR. f/awaea M 65% 5 AWAJ C, 5% Ms flrroem'f N A r .R mm u H.M. GEYER Oct. 11 1960 HYDRAULIC ACTUATOR HAVING COOLING FLUIDCIRCULATION Filed Jan. 15, 1958 4 Sheets-Sheet 3 INVENTOR. Hon/41w M665458 J m I M5 firraezvir UnitedStates Patent Ofiice 2,955,574 PatentedOct. 11, 1960 HYDRAULIC ACTUATOR HAVING COOLING FLUID CIRCULATION FiledJan. 13, 1958, Ser. No. 708,490

Claims. (Cl. 12138) This invention pertains to actuators, andparticularly to synchronized hydraulic actuators designed for use inhigh ambient temperatures.

It is well recognized that hydraulic actuators which are subjected tohigh ambient temperatures in the range of 1000 F. must include means forcirculating hydraulic fluid throughout the parts exposed to such ambienttemperatures to effect cooling thereof. The. present invention relatesto a linear actuator assembly designed for synchronous operation withother like actuators including self-cleaning orifice means forcontrolling the metered flow of circulating hydraulic cooling fluid.Accordingly, among my objects are theprovision of a hydraulic actuatorassembly including means for circulating cooling fluid throughoutsubstantially the entire length of the piston rod; the further provisionof a hydraulic actuator including metallic piston rings constituting ametering orifice for the circulation of cooling fluid; and the stillfurther provision of an actuator assembly including tandem arrangedpistons and means for circulating cooling fluid through the exposedpiston rod thereof.

The aforementioned and other objects are accomplished in the presentinvention by incorporating an oil circulation tube in the actuatorassembly and pressure drop orifice means for the circulation of coolingoil through the tube. Specifically, the actuator assemblies of thisinvention constitute improvements over the actuator assembly disclosedin my copending application Serial No. 681,033, filed August 29, 1957.Moreover, two embodiments of an improved actuator assembly aredisclosed, the first embodiment including a cylinder having areciprocable piston disposed therein. The piston includes a rod whichextends without the cylinder for attachment to a movable load device,the cylinder being attached to a fixed support. The piston carries a nutwhich engages a screw shaft, or rotatable member, such that pistonreciprocation is dependent upon rotation of the screw shaft. The screwshaft is adapted for connection through gearing to a rotarysynchronizing shaft which interconnects adjacent like actuators. Thepiston rod carries a pair of metallic piston rings, which are assembledwith the actuator by first placing a sleeve thereover, the sleeveconstituting an assembly tool, and thereafter remaining within theactuator cylinder. The piston rings constitute pressure drop orificemeans, and the rod has disposed therein a coaxial tube such that oilflowing between the piston rings and the cylinder can flow through a rodopening to the space between the tube and the inner surface of the rod.

The oil circulation cooling tube terminates short of the outer end ofthe rod such that cooling fluid can pass through the tube and backthrough the piston to the other actuator chamber. In addition, the rodend of the cylinder includes a pressure drop bushing as well as lowpressuremetallic seals, the outlet side of the pressure drop bushingbeing connected to a drain circulation line.

In the second embodiment the actuator assembly includes a pair ofpressure drop bushings, a pair of pistons arranged in tandem and apiston rod which extends Without the cylinder. One of the pistons isoperatively connected to a screw shaft such that pistonreciprocation isagain dependent upon rotation of the screw shaft. The external pistonrod likewise has an oil circulation tube coaxially disposed thereinwhereby oil leakage past the pressure drop bushing passes throughoutsubstantially the entire length of the rod before returning to theactuator chamber having the lower pressure potential.

Further objects and advantages of the present inven tion will beapparent from the following description, reference being had to theaccompanying drawings, wherein preferred embodiments of the presentinvention are clearly shown.

In the drawings:

Figure 1 is a perspective view, partly in section and partly inelevation, of an actuator assembly constructed according to oneembodiment of this invention.

Figure 2 is a fragmentary view, partly in section and partly inelevation, of an actuator constructed according to the second embodimentof this invention.

Figure 3 is a fragmentary sectional view of'the actuator assemblyconstructed according to the second embodiment of this invention.

Figures 4 and 5 are enlarged fragmentary sectional views of the pressuredrop bushings 98 and 82, respectively, of Figure 3.

With particular reference to Figure 1, an actuator assembly is shownincluding a cylinder 10 having an integral axially extending skirtportion 11 at the rod end thereof. The head end of the cylinder isclosed by a cap 12 having a fixture 13 by which means the actuator canbe attached to a fixed support, not shown. The cylinder 10 has disposedtherein a reciprocable piston 14 having a pair of metallic piston ringseals 15, the piston 14 dividing the cylinder 10 into an extend chamber16 and a retract chamber 17. The piston carries a nut 18 whichthreadedly engages a screw shaft 19 attached to a worm gear 20. The wormgear 20 is rotatably journalled with the cylinder 10 by ball bearingassemblies 21, and reciprocation of the piston 14 is dependent upon andeffects rotation of the screw shaft 19.

In accordance with the teachings of my Patent 2,657,- 639, the worm gear20 meshes with a worm 22 attached to a rotary synchronizing shaft 23,which may be of the flexible type. The synchronizing shaft 23 isutilized to interconnect the rotatable members, or screw shafts, ofadjacent like actuators so as to synchronize their movements. Inaddition, synchronizing shaft 23 is enclosed by a conduit 24 throughwhich hydraulic fiuid under pressure can be admitted or drained from theextend chamber 16.-

The piston 14 has an integral hollow rod 25 that extends wi-thout thecylinder. The rod has a closed outer end and can be connected to anysuitable movable load device, not shown. The actuator is installed sothat neither the cylinder nor the piston can rotate, and hence, it istermed a linear actuator. The piston rod carries a pair of piston ringtype seals 26, which constitute selfcleaning orifice means since theypermit a metered amount of fluid flow between the rod and the cylinderdue to a pressure differential thereacross. The orifice means are termedself-cleaning since any foreign ma terial which may become lodgedbetween the piston rings 26 and the skirt 11 will be automaticallyremoved during reciprocation of the piston rod relative to the cylinder.The piston rings are maintained in assembled relation with the rod 25 bya sleeve 27 prior to insertion of the piston and rod assembly into thecylinder. However, after assembly of the piston rod in the skirt 11 ofthe cylinder, the sleeve 27'remains in the retract chamber, as shown inFigure 1. The retract chamber 17 is connected through a porting block 28to a retract conduit 29 through which fluid under pressure may beapplied or drained from the retract chamber 17.

The piston rod 25 has an oil circulation tube 30 press fitted therein,the major portion of the oil circulation tube 30 being of a lesserdiameter than the hollow piston rod so as to form an annular channel 31between the tube and the inner surface of the hollow piston rod. Theannular channel 31 connects with the right hand side of the piston ringseal 26 through a radial passage 32. The circulation tube 31 terminatesshort of the closed outer end of the hollow piston rod, and the innerend of the tube 30 connects with the extend chamber 16 through passagemeans in the piston similar to those disclosed in the aforementionedcopending application.

In addition, the rod end of the cylinder is fitted with a pressure dropbushing 33 as well as metallic low pressure seals 34 and 35 which areretained in position by a nut 36. The outlet side of the pressure dropbushing 33 communicates with an annular groove 37 which connects with aporting block 38 and a drain conduit 39. The porting block 38 isattached to the rod end of the cylinder by a U-shaped clamp 40, the endsof which are threaded to receive nuts, such as indicated by numeral 41.

Operation of the actuator aforedescribed is as follows.

Upon application of pressure to the extend chamber 16 while the retractchamber 17 is connected to drain, the piston 14 will move outwardly asviewed in Figure 1 thereby eflecting rotation of the screw shaft 19. Apredetermined amount of fluid from the extend chamber 16 will flow intothe hollow rod 25 through passages 18a formed by longitudinal serrationsin the nut as seen in Figure la, through the tube 30, to the outer endof the rod 25 and thence through the annular channel 31 thereby coolingsubstantially the entire length of the piston rod. This cooling fluidwill flow to drain through the passage 32, past the piston ring typeorifice means 26 which control the amount of circulating cooling fluid,and thence to the retract chamber 17 which is connected to drain. Anycooling fluid which does not pass through the orifice means 26 will flowoutwardly to the annular groove 37 and thence through the porting block38 to the drain conduit 39.

Conversely, when the retract chamber is subjected to pressure while theextend chamber is connected to drain, a predetermined quantity of oilwill flow past the pressure drop bushing piston ring type sealing means26 through the passage 32, to the annular groove 31 and thence throughthe tube 30 and back to the extend chamber 16. Some fluid will also flowbetween the rod 25 and the skirt 11 to the annular groove 37 and thenceto the drain line 39.

With particular reference to Figures 2 and 3, a second embodiment of ahydraulically cooled synchronized actuator will be described. In thesecond embodiment, the actuator includes a cylinder 50 having a head endcap 51 secured thereto by means of a nut 52. The cylinder 50 has a pairof porting blocks 53 and 54 attached thereto by U-shaped clamps 55,having threaded ends which receive nuts 56. As seen particularly inFigure 3, the head cap 51 has a fixture 57 attached thereto whereby thecylinder may be attached to a fixed support, not shown. In addition, aWorm gear 58 is rotatably journalled within the head cap 51 by means ofa ball bearing 59 and 60. The worm gear 58 meshes with a worm 61 whichmay be attached to a flexible synchronizing shaft enclosed Within aconduit 62. The conduit 62 is used to supply and drain oil to theactuator extend chambers, as will be described hereinafter.

In the actuator assembly of the second embodiment, a tandem pistonarrangement is utilized enabling the use of a smaller diameter cylinder.Thus, the cylinder 50 has disposed therein a pair of pistons 63 and 64having metallic pinion ring seals 65 and 65', respectively. The

piston 63 is integral with a hollow rod 66 which is threadedly connectedat 67 to the piston 64. In addition, the piston 63 carries a nut 68which threadedly engages a rotatable screw shaft 69 connected to theworm gear 58. Accordingly, reciprocation of the piston 63 and the piston64 is dependent upon rotation of the screw shaft 69. The nut 68 isformed with external serrations so as to form passages 70 for the flowof circulating cooling fluid through the piston 63.

The piston 63 divides its portion of the cylinder into an extend chamber71 and a retract chamber 72, the cylinder being divided into twoportions by a pressure drop bushing 98. Likewise, the piston 64 dividesits portion of the cylinder into an extend chamber 73 and a retractchamber 74. The extend chambers 71 and 73 are interconnected by aconduit 75, and the retract chambers 72 and 74 are interconnected by aconduit 76. One end of the conduit 75 connects with the conduit 62 andthe other end of the conduit 75 connects with the porting block 53 andthence through a passage 77 to the extend chamber 73. Conduit 62 isconnected to extend chamber 71 through passage 97. One end of theconduit 76 connects with the porting block 53 and through a passage 78to the retract chamber 72. The conduit 76 also connects to a conduit 79in the porting block 53. The other end of the conduit 76 connectsthrough a passage 80 in the porting block 54 to the retract chamber 74.In addition, the porting block 54 is connected to a drain line 81.

The pressure drop bushing 98 slidably supports the piston rod 66, itbeing understood that there is a slight annular clearance 98a, as seenin Figure 4, between the inner diameter of the pressure drop bushing andthe piston rod 66 constituting a self-cleaning orifice. The latterorifice is termed self-cleaning since any foreign material which maybecome lodged between the pressure drop bushing 98 and the piston rod 66will be automatically removed upon reciprocation of the piston rodrelative to the cylinder and the pressure drop bushing 98. The rod endof the cylinder likewise includes a pressure drop bushing 82, the outletside of which connects with a radial passage 83 and the drain line 81.There is also a slight annular clearance 82a between the rod 84 and thepressure drop bushing 82, as seen in Figure 5, constituting aself-cleaning orifice.

The piston 64 also includes an integral hollow rod 84 having a closedouter end. The piston rod 84 is adapted for connection to a movable loaddevice and extends outside of the cylinder. In addition, the piston rod84 has attached thereto a sleeve 85. with a flanged end 86telescopically disposed within a reciprocable sleeve 87 having flangedends 88 and 89. The slidable sleeve 87 is disposed within an outer heatshield 90 having a flanged end 91. During outward movement of the pistonrod 84, as viewed in Figure 3, the flange 86 will engage the flange 88with sleeve 87 and thereby move the sleeve 87 out- Wardly until theflange 89 engages the flange 91 of the heat shield 90. The heat shield90 is attached to the cylinder 50 by a threaded coupling 92. Inaddition, the rod end of the cylinder 50 includes three metallic lowpressure seals 93.

The hollow rod 84 has disposed therein an oil circulation tube 94, theinner end of which is snugly received wittnn the hollow piston rod 66.The outer end of the rod 94 has a plurality of radial ports 95 therein,the rod 94 terminating short of the closed outer end of the rod 84. Thetube 94 is utilized to circulate cooling fluid throughout substantiallythe entire length of the piston rod 84 to eflect cooling thereof.

Operation of the tandem piston actuator is as follows. When the extendchambers 71 and 73 are subjected to fluid under pressure while theretract chambers 72 and 74 are connected to drain, a predeterminedquantity of oil will flow from the extend chamber 71 through the passage70, the hollow rod 66 to the tube 94 so as to cool the rod 84. Thereturn flow of the cooling oil is through holes 95, and the annularspace 96 between the tube 94 and the hollow rod 84. This cooling oilwill flow through groove 99 between the tube 94 and the outer end of rod66 through radial passages 100 in the rod 66 and thence through theannular clearance between the pressure drop bushing 98 and the rod 66 toretract chamber 72 which is connected to drain. During application ofpressure fluid to the extend chambers, pisgons and 64 will move to theright as viewed in Figures When pressure is applied to retract chambers72 and 74 while the extend chambers 71 and 73 are connected to drain,oil will flow from the retract chamber 72 through the orifice means topassages 100 and thence through the passage 99 to the channel 96. Thiscooling oil will flow to the outer end of the rod through passages 95and thence through the tube 94 to the hollow piston rod 66 to the extendchamber 71 through the passage 70. At this time, a predeterminedquantity of oil will also flow past the pressure drop bushing 82 to theannular groove 83 and thence to the drain line 81. During theapplication of pressure to the retract chambers, of course, the pistons63 and 64 will move to the left as viewed in Figure 3.

While the embodiments of the invention as herein disclosed constitute apreferred form, it is to be understood that other forms might beadopted.

What is claimed is as follows:

1. An actuator assembly including, a cylinder, a pair of tandem arrangedreciprocable pistons disposed in said cylinder capable of fluid pressureactuation in both directions, one of said pistons having a hollow rodwith a closed outer end extending from said cylinder, the other of saidpistons having a rod connected to said one piston, self-cleaning orificemeans between one of said rods and said cylinder, and means directingthe flow of fluid through said orifice means throughout substantiallythe entire length of said hollow piston rod to effect cooling thereof.

2. An actuator assembly including, a cylinder, a pair of tandem arrangedreciprocable pistons disposed in said cylinder capable of fluid pressureactuation in both directions, one of said pistons having a hollow rodwith a closed outer end extending from said cylinder, the other of saidpistons having a hollow rod attached to said one piston, a memberrotatably journalled in said cylinder and operatively connected with oneof said pistons whereby piston reciprocation effects rotation of saidmember, selfcleaning orifice means between said cylinder and one of saidrods, and means directing the flow offluid through said orifice meansthroughout substantially the entire length of the hollow piston rod toeffect cooling thereof.

3. A fluid pressure operated actuator, including, a cylinder, a pair oftandem arranged reciprocable pistons disposed in the cylinder, one ofsaid pistons having a hollow rod extending from the cylinder with aclosed outer end, the other piston having a hollow rod attached to saidone piston, a member rotatably supported in said cylinder andoperatively connected to said other piston so as to rotate upon pistonmovement, a pair of spaced self-cleaning orifice means between thecylinder and said rods permitting a metered flow of fluid therebetweendue to a pressure differential across said orifice means, said pistonsdividing the cylinder into pairs of opposed chambers, one end of eachorifice means connecting with one pair of said chambers, meansconnecting the other end of one of said orifice means to the interior ofone of said hollow rods, and means including a tube disposed within oneof said hollow rods for connecting the outer end of said extendinghollow piston rod with one of said other pair of actuator chambers.

4. An actuator assembly including, a cylinder, a pair of tandem arrangedreciprocable pistons disposed in the cylinder capable of fluid pressureactuation in both directions, means dividing said cylinder in two parts,each piston dividing its part of the cylinder into an extend chamber anda retract chamber, one of said pistons having a hollow rod extendingfrom said cylinder with a closed outer end, the other piston having ahollow piston rod attached to said one piston, said means dividing saidcylinder into two parts comprising self-cleaning orifice means betweensaid cylinder and the rod attached to the other piston, one end of saidorifice means connecting with the retract chamber of one cylinder partand the other end of the orifice means connecting with the extendchamber of the other cylinder part, passage means connecting the otherend of the said orifice means with the interior of said hollow rodhaving a closed outer end, a tube disposed within said hollow rod andhaving an end spaced from the closed outer end of said rod, and throughwhich fluid passing through said orifice means to the outer end of therod can flow, and passage means connecting the interior of said tubewith the extend chamber of one of said cylinder parts, said orificemeans permitting metered flow of fluid due to a pressure differentialthereacross which flow of fluid cools substantially the entire length ofsaid hollow rod having the closed outer end.

5. A fluid pressure operated actuator including, a cylinder, areciprocable piston in the cylinder having a hollow rod extendingtherefrom with a closed outer end, a member rotatably supported in saidcylinder and operatively connected to said piston so as to rotate uponpiston movement, self-cleaning piston ring type orifice means betweenthe cylinder and the rod permitting metered flow of fluid therebetweendue to a pressure diflerential across said orifice means, said pistondividing said cylinder into opposed chambers, one end of said orificemeans communicating with one of said chambers, means connecting theother end of the orifice means to the interior of said hollow rod, meansincluding a tube disposed within said hollow rod connecting the outerend of said hollow rod with the other actuator chamber, and a sleeveslidably engaging said piston rod and disposed within one of saidactuator chambers, said sleeve being utilized during assembly of the rodwith the cylinder for retaining the piston ring type orifice means inposition.

References Cited in the file of this patent UNITED STATES PATENTS2,217,239 Smith Oct. 8, 1940 2,688,313 Bauer Sept. 7, 1954 2,806,450Geyer Sept. 17, 1957

